The invention relates to a follower fall arrest device used with a fixed safety rope, and comprising:
a body equipped with a securing system arranged to occupy either an active locking position in case of a fall or an inactive unlocking position enabling the user to progress along the rope in the ascending direction, or in the opposite direction when performing a controlled descent, said securing system comprising a support arm articulated on a first spindle of the body, a roller in the form of a cylindrical wheel mounted rotating free on a second spindle securedly attached to the support arm, and a centrifugal clutch mechanism arranged between a drive member of the roller and the support arm so as to occupy a disengaged position or an engaged position,
and attachment means for connecting the body to a safety harness worn by the user.
In normal use for ascending or descending, fall arrest devices follow the progression of the person along the rope without causing any seizure. The person is free to move without any manual unlocking action on the fall arrest device. Locking only takes place in case of a fall.
The securing system of known fall arrest devices generally comprises a pivoting lever having an attachment ring at one of the ends thereof for connection to a harness, and a cam for jamming the rope at the opposite end thereof. Such an arrangement acts as a jamming cleat, which is liable to prevent locking if the user grabs the lever in case of a fall.
The document WO 00/24471 relates to a two-way locking device for a fall arrest device comprising a locking member equipped with two cams actuated in independent manner by a common disabling member in reaction to a sudden change of weight. Locking of each of the cams depends on the angle of incline of the rope with respect to the frame of the device.
The document U.S. Pat. No. 4,923,037 describes a fall arrest device having a securing system composed of an articulated support arm which is equipped with a cylindrical wheel mounted with free pivoting and a centrifugal clutch mechanism arranged as a pawl. The periphery of the wheel comprises a series of teeth forming a sprocket causing rotation of the wheel by friction effect with the rope. The radial direction of the teeth does not enable optimum operation of the fall arrest device to be obtained. Moreover, to insert the vertical lifeline in the fall arrest device, it is necessary to make use of an articulated U-shaped angle bracket and to make it pivot outwards, which complicates operations.
The object of the invention is to provide a fall arrest device for a fixed rope enabling maximum safety to be achieved for the user in case of a fall, regardless of the angle of incline of the rope or of a handling error of the equipment.
The fall arrest device according to the invention is characterized in that the peripheral surface of the roller is equipped with a plurality of studs arranged to cause rotation of the roller in the descending direction, and sliding on the rope in the ascending direction, and that the body comprises a straight U-shaped channel for passage of the rope, said channel having holes for passage of the attachment means.
In normal use for ascending or descending, the clutch mechanism is in the disengaged position, and the fall arrest device follows the progression of the person along the rope without any manual unlocking action of the securing system. Locking takes place automatically in case of a fall even if the user doesn""t seize the device. In this case, the clutch mechanism is in the engaged position resulting in a strong pressure being exerted by the roller against the rope.
According to a preferred embodiment, the clutch mechanism is arranged inside the roller and comprises at least one flyweight movable by centrifugal effect along a ramp according to the speed or the acceleration of the drive member of the roller. The flyweight is associated with a return spring urging the clutch mechanism to the disengaged position, the coupling threshold being reached when the centrifugal force is greater than the return force of the spring.
It is naturally possible to use any other type of engagement device designed to lock the roller on the support arm at a predetermined speed.
Other features can be used either separately or in combination:
the flyweight is cylindrical in shape and cooperates in the engaged position with a cylindrical rim of the support arm;
the attachment means are formed by a karabiner passing through aligned holes of the body of the fall arrest device;
the support arm is equipped with safety means designed to limit the pivoting travel of said arm in the inactive unlocking position and to prevent the karabiner from being fitted before the rope has been inserted in the channel;
the safety means comprise a stop securedly attached to the support arm and having one end equipped with a protuberance;
the safety means comprise a flap pivotally mounted on a spindle and comprising an oblong opening inside which an operating lever securedly attached to the support arm moves, and a wing designed to press the rope against the bottom of the channel.